The invention relates to a method for processing various materials, the method including grinding at least one material, mixing the material with another material and extruding the mixture of materials into a product.
The invention further relates to an apparatus for processing material, including at least two annular feed gaps placed one within the other.
RU 2,049,550 discloses a grinder comprising a conical rotor and a conical stator. This apparatus is able to grind input material, but the ground material requires further processing to provide an actual product.
U.S. Pat. No. 5,624,616 discloses a method for making fibre products. In this arrangement, wood and a polymer are mixed at a high temperature and pressure in order to soften the wood lignin. However, this arrangement is rather complicated and difficult to implement.
An objective of the present invention is to provide a method and an apparatus for efficient processing of material.
The method according to the invention is characterized by processing the materials simultaneously in an apparatus provided with a grinding section and a mixing section, so that at least in the grinding section the apparatus is provided with at least two annular feed gaps placed one within the other, and at least one material is ground in the feed gap, and mixing the materials in the mixing section of the apparatus after the grinding.
Further, the apparatus according to the invention for processing material is characterized in that the beginning of at least one feed gap is provided with a grinding section, which is followed in the apparatus by a mixing section for mixing together the materials that used to be in different feed gaps.
According to a basic idea of the invention, the apparatus comprises at least two annular feed gaps placed one within the other. The beginning of at least one feed gap is provided with a grinding section that can also be used for melting if the material is meltable. The grinding section is followed in the apparatus by a mixing section for mixing the materials that used to be in different feed gaps. The basic idea of a preferred embodiment is that the feed gaps are shaped like tapering cones in order to increase the pressure in the grinding section towards the end thereof. According to another preferred embodiment, the surfaces of the rotor and the stator situated on different sides of the feed gap in the grinding section are wavelike, and the grooves of the rotor and the stator are formed such that when the rotor groove is the deepest the stator groove is the shallowest and vice versa. According to a third preferred embodiment, the mixing section comprises, between the feed gaps, a rotor provided with openings for mixing together the materials in the different feed gaps. According to a fourth preferred embodiment, different materials are fed into different feed gaps, i.e. a non-melting material is supplied to the first feed gap and a material that melts in the grinding section is fed into the second feed gap, the materials being mixed in the mixing section so that the obtained mixture is sufficiently viscoelastic to be extrudable out of the apparatus. According to a fifth preferred embodiment, a wood material is fed into the first feed gap and ground, pulverized into fibres and simultaneously during grinding substantially dehydrated. A polymer is fed into the second feed gap, melted in the grinding section and mixed in the mixing section with the dry wood fibres, whereafter the mixture is extruded into a product.
The invention provides the advantage that one apparatus is sufficient to grind the material and to form an actual product. With conical feed gaps it is possible to increase the pressure in the grinding section, so that the apparatus can be used e.g. to dehydrate the material to be ground. When the surfaces of the rotor and the stator located on different sides of the feed gap are wavelike and the rotor and stator grooves are formed such that the rotor groove is the deepest when the stator groove is the shallowest and vice versa, the structure provides highly efficient grinding and shearing of the material between the rotor and the stator. The apparatus enables efficient processing of non-melting material and melt material simultaneously supplied thereto, thus providing various products with good properties. The grinding section can also be followed by a decompression zone, where the rest of the moisture, which is e.g. in the form of steam or some other gas, can be discharged from the apparatus via openings provided in the stator.